Technical LHD 2021 Knaus L!ve Wave 700 Meg: Repairing back "bumper"

[Nenagh52]

So ,some damage

and

I have the missing piece, the wires held it and its now in the garage.
Can I remove the "back bumper" from the outside or do I need to remove some panels in the garage.
Any suggestions on how to stick the plastic.
Thanks as always